In a large-scale network, the cost of laying cables becomes an issue; for instance, there is an example of a supercomputer using cables as long as 1,000 km. When cables are installed with such high density, it becomes difficult to move the wring of the cable, reconnect cable terminals, or exchange cables.
Therefore, as an alternative to the cable, wireless communication in which connection changes can easily performed may be utilized. For instance, a wireless link using conventional and general radio waves such as the 2.4 GHz band can be utilized. Furthermore, as a high-speed wireless technology that can be used in high density, the study of optical space communication, which is wireless communication using an optical signal, has made progress. In optical space communication, it is possible to arrange wireless links with ultra-high density since optical beams do not interfere with each other as long as narrow optical beams are used. The utilization of such a high-speed wireless link is expected to provide a link that can be easily set up in a large-scale network.
Patent Literature 1 discloses a communication protocol selection apparatus and method for a router for forwarding a packet that prevent packet loss and communication failure in a network and enable the construction of a highly reliable communication system. More concretely, Patent Literature 1 describes a configuration in which storage means for storing the communication protocol type of an access router that corresponds to a user address is provided, protocol request means for giving the user address of a destination user to a first access router and for transmitting a protocol request signal that requests the communication protocol type of a second access router accommodating the destination user is provided, and protocol management means for reading the storage means when the protocol request signal is received and for returning the communication protocol type of an access router that corresponds to a user address transmitted by the protocol request means is provided.
Patent Literature 2 discloses a network controlling system enabling common network management when a plurality of wireless systems are accommodated by a common network. The document states that a node provided on the network comprises transmitting/receiving means that transmits and receives a control signal defined by each of the wireless systems, protocol converting means that converts the control signal to a common protocol independent of each of the wireless systems, and entity communication controlling means that communicates with a functional entity implementing network control, using the converted common protocol.
Non-Patent Literatures 1 and 2 propose a centralized control type communication system called OpenFlow. OpenFlow treats communication as an end-to-end flow and performs path control, failure recovery, load balancing, and optimization for each flow.